Motion transforming device for electronic timepieces and the like



Nov. 17, .1970 M. HETZ EL 3,540,205

MOTION TRANSFORMING DEVICE ,FOR ELECTRONIC TIMEPIECES AND THE LIKE Filed March 25, 1969 3- Sheets-Sheet l ulllmuullululunuufl Nov. 17,1970 M. HETZEL 3,540,206

MOTION TRANSFORMING DEVICE FOR ELECTRONIC TIMEPIECES AND THE LIKE Filed March 25, 1969' 3 Sheets-Sheet 2 Nov. 17, 1970 M. HETZEL 3,540,206

' v MQTION TRANSFORMING DEVICE FOR ELECTRONIC TIMEPIECES AND THE LIKE Filed March 25, 1969 3 Sheets-Sheet 5 29 21 mag E v 4 H 1 I111]! 11 I1 11 n n u n n m n n n Inn United States Patent US. Cl. 5823 13 Claims ABSTRACT OF THE DISCLOSURE In a time measuring device wherein an acoustical resonator constitutes the time keeping standard and wherein a motion transformer having a pawl fixedly attached to the resonator engages the teeth of a ratchet wheel to transmit rotary impulses thereto and drives a gear train of the type indicated, there is provided a magnetic coupling arranged between'the ratchet wheel and the gear train to smooth out intermittent rotation and transform it into an at least approximately continuous motion, the coupling being described as including a driving wheel having a circumferential region of magnetizable poles mounted so as to surround coaxially the axis of the ratchet wheel, the number of teeth on the ratchet wheel being greater than the number of poles of this region; a driven wheel with magnetizable poles disposed around its periphery and adjacent the driving wheel so as to bring together the effective range of some poles of one wheel within the effective range of some poles on the other wheel and means for magnetizing said driving and driven wheels.

This application is a continuation-in-part of my copending application Ser. No. 539,852, filed Apr. 4, 1966, now patent No. 3,451,280.

The present invention relates to time measuring devices comprising a mechanical resonator operative in the acoustic frequency range serving as a time keeping standard as well as driving the gear system of a time indicator through a pawl-ratchet wheel-gear system serving to transform oscillatory motion into rotary motion. In such devices the pawl secured to the resonator undergoes great acceleration which is transferred also to the ratchet wheel and to all other component parts which are kinematically coupled to the ratchet wheel. If the masses to be accelerated are too great, corresponding reactive forces react through the pawls and on to the resonator. Such reactive forces disturb the unhampered vibration of the resonator and affect the pawl. For that reason, the masses to be accelerated must be kept as small as possible.

The invention provides therefore a magnetic coupling for connecting the ratchet wheel with the gear works for transforming the intermittent rotation of the ratchet wheel into a merely continuous rotary motion. But the force to be transmitted in such a coupling, from its driving part to its driven part, is limited by the magnetic strength of the material and its size, being very small in a wristwatch. Therefore there is the difficulty that sometimes the driven part is disengaged of the driving part of the coupling if the driving part is subject to a high periodic acceleration and if the driven part has a large mass. In the timing device, however, the rotation of a timing and indicating means must equal the frequency of the ratchet wheel.

The principal object of the present invention is to overcome many of the drawbacks found in presently used time measuring devices by providing a magnetic coupling arranged between the ratchet wheel and the gear train of a time measuring device, comprising a driving wheel having a circumferential region of magnetizable poles mounted to surround coaxially the axis of the ratchet wheel, the number of teeth of the ratchet wheel being greater than the number of poles of this region; a driven wheel having magnetizable poles disposed around its periphery, adjacent to the driving wheel, so as to bring together the effective range of some poles of one wheel with the effective range of poles of the other wheel, and means for magnetizing the driving and driven wheels.

Advantageously the number of teeth on the ratchet wheel is greater than six times the number of poles of the driving wheel. In particular, the number of teeth of the ratchet wheel can be from about 10 to times but preferably from about 25 to 60 times greater than the number of poles on the driving wheel. Normally in wrist watches the frequencies of the resonator are higher than 300 oscillations/ second.

With the invention the rotational speed in the coupling is relatively high and the energy transferred at every rotation is relatively small. Therefore the coupling forces transmitted from the driving part to the driven part is small. Because in the effective range of one pole on the driven wheel, the driving wheel is accelerated many times in alternating directions, there cannot be any interruption of the force between the poles during one single acceleration of the driving wheel. Otherwise if the number of poles on the driving wheel and the number of teeth of the driven wheel are almost equal, there will occur slipping because the force may break down, or if the force is high enough all the gear wheels will always be kept accelerated.

The present invention will be better understood by referring to the accompanying drawings showing schematic forms of executions in which:

FIG. 1 is a plan view of one device according to the invention;

FIG. 2 is an elevational view of another form of the invention;

FIG. 3 is a plan view of still another embodiment of the invention employing coupling wheels of magnetic soft material and a permanent magnetical bar or yolk between the axes of the driving and the driven wheels;

FIG. 4 is a fragmentary elevation view thereof;

FIGS. 5 and 6 are elevational views of other embodiments.

The resonator fragmentarily shown at 1 has a given a1- ternating movement along arrow 2. It carries a first pawl formed of a blade 3 and a ruby pallet 4. The latter drives a ratchet wheel 5 having a large number of teeth, for example, 240 teeth.

A second pawl fixed to the frame of the watch and constituted by a blade 6 carrying at its free extremity a ruby pallet 7, serves as a stop pawl for immobilizing the wheel 5 when it is not driven by the resonator.

A non-magnetic shaft 8a of the wheel 5 carries a rim 8 diametrically or transversely magnetized so as to provide three pairs of poles with alternate polarity south (S) and north (N). This wheel 8 may be constituted of an alloy of platinum and cobalt of very high magnetic strength. When it turns, the magnetized polar wheel 8- drives a wheel 10 constituting the first wheel of the gear train and having a larger diameter than the wheel 8. The wheel 10 is also diametrically magnetized and comprises equally distributed poles, N, S, of alternative polarity along its circumferential region surrounding its axis. The number of poles of wheel 10 is greater than the number of poles of wheel 8. The gap between opposite poles of both wheels is smaller than the distance separating two adjacent poles of either wheel, preferably by an order of magnitude smaller than said distance.

The present device for transforming the movement has the advantage of being very simple, of avoiding to a large degree losses of power due to friction, and of constituting an excellent mechanical filter for isolating the resonator from the gear train. Moreover, the mechanical tolerance of the wheels 8 and 10 can be much lower than that of wheels which are assigned for mechanical engagement. Thus it is possible to make entirely independently, on the one hand, the oscillator with its device for transforming the movement comprising the pawl, the ratchet wheel and its polar wheel 8 and on the other hand the gear train mounted on the plate and including the wheel 10, and to assemble then without difficulty these initially independently assembled construction units. Moreover, the gap tolerance is not critical which simplifies the assembling.

The wheel 10 can be made of a suitable ferro-nickel alloy.

In FIG. 2, a shaft 11 of a ratchet wheel 13 constitutes the permanently magnetized driving wheel cooperating with the driven wheel 12. For this purpose, the shaft 11, which suitably can have a diameter of only about 0.3 mm. is diametrically magnetized over its entire length so as to form one pair of elongated poles N and S as schematically shown in FIG. 2.

The distance separating the poles of wheel 12 is about 1.2 times the diameter of the shaft 11 which is made, for example of an alloy of platinum and cobalt which has a high magnetic and mechanical strength. The ratchet wheel 13 may be of a copper-beryllium alloy.

In the embodiment of FIGS. 3 and 4 there are used a wheel 15 and a second wheel 16 which have projecting teeth forming magnetizable poles. One wheel 15 can have an external diameter of 0.6 mm. and for example six teeth.

Both wheels 15 and 16 are made of soft magnetic material and their magnetism results from a permanent magnet such as a pole magnet or magnetic yoke 19 placed between the shafts 17 and 18 of these wheels, and imparts oppositely directed magnetization to the two wheels, so that the magnetic flux forms a closed loop from pole N of the magnetic yoke 19 to the shaft 17, pole N of wheel 15, the gap between both wheels, the opposite lying pole S of wheel 16, the shaft 18 of wheel 16 and pole S of the yoke 19. All the air gaps are very small as compared with the distance separating adjacent poles from either wheel 15 or 16. Preferably, the flux provided in this embodiment of the invention is of 10,000 or more gauss. The magnetic yoke 19 can be made of an inexpensive magnetic material because no special properties are required. Similarly the yoke can be made of different shapes, for example U-shape with opposite ends adjacent to the undersides of the shaft 17 and 18.

All the constituent parts of the coupling can be very small so as to be suitable for use in small electric watches.

The embodiment according to FIGS. 34 can be modified to provide another useful effect, as shown in FIGS. 5 and 6.

' In the embodiment shown in FIG. 5, a shaft 20 has mounted thereon a driving wheel 28 and a ratchet wheel 29. A shaft 31 has mounted thereon a driven wheel 38. Both shafts 20 and 31 are slidably supported, that is to say they are axially movable relative to respective radial bearings 23 and 37 and axial bearings 24 and 33 at the lower ends of the shaft end which consist of a setting 25 and 34 each having a through stone 26' and and an end stone 27 and 36 carrying the pivots 21 and 32 of the shafts.

All the bearings are inserted in a thick bridge member 22. Stops 30 and 39 are provided on the other ends of the shafts to limit the possible displacement of shafts 20 and 31 due, for example, to shocks. Magnet provides for the magnetization of the shafts and also gives a downwardly directed magnetic attraction to hold the shafts in the bearings 24 and 23, the pivots 21 and 32 being kept in contact with the end stones 27 and 36. Another magnet 41 between both shafts serves to increase the magnetic flux.

In this embodiment the shafts can be simply mounted by axial movement into the bearings 23, 37 respectively; and it can similarly be removed.

In a varient of this embodiment, member 40 is made of a soft magnetic material and is magnetized from magnet 41 through the shafts 20 and 31.

In the embodiment of FIG. 6, magnet 41 is dispensed with and a permanent magnetic yoke 61 is used for both functions. Here there are no radial bearing as in FIG. 5 and only normal bearings 53, 54, 59 and .60 respectively are used in two thin bridges 55, 56, the driving wheel 52 and the ratchet wheel 51, being on shaft 51 and the driven wheel 58, cooperating with wheel 52, being on shaft 57.

In all of the described embodiments, the number of teeth for the driven wheel is greater than the number of poles of the driving wheel, so that each has an effective coupling range which corresponds to a greaternumber of teeth of the ratchet wheel.

Having thus disclosed my invention I therefore particularly point out and distinctly claim as my invention:

1. In a time measuring device wherein an acoustical resonator constitutes the time keeping standard and wherein a motion transformer, having a pawl fixedly attached to resonator and engaging teeth of a ratchet wheel to transmit rotary impulses thereto, drives a gear train of a time indicator; a magnetic coupling arranged between said ratchet wheel and said gear train to smooth out intermittent rotation and transform it into an at least approximately continuous rotatory motion, comprising:

(a) a driving wheel having circumferential region of magnetizable poles mounted to surround coaxially the axis of said ratchet wheel, the number of teeth on the ratchet wheel being greater than the number of poles of this region,

(b) a driven wheel having magnetizable poles disposed around its periphery, adjacent the driving Wheel so as to bring together the effective range of some poles of one wheel within the effective range of some poles of the other wheel, and

(0) means for magnetizing said driving and driven Wheels.

2. Device as set forth in claim 1, wherein at least one of said wheels contains material of high magnetic strength and permanently magnetized poles.

3. Device as set forth in claim 1, wherein the driving and the driven wheels are of soft magnetic material having projecting teeth forming magnetizable poles and a permanent magnet disposed adjacent the shafts of said wheels, so as to magnetize both said wheels by different magnetic poles.

4. Device as set forth in claim 1, wherein the number of teeth of said ratchet wheel is more than six times the number of poles of said driving wheel.

5. Device as set forth in claim 1, wherein the number of teeth of said ratchet wheel is between ten and a hundred times greater than the number of poles of said driving wheel.

6. Device as set forth in claim 1, wherein the axis of said driven wheel is at least approximately parallel to and spaced from said axis of said ratchet wheel.

7. Device as set forth in claim 1, wherein the diameter of said driven wheel is larger than the diameter of said driving wheel.

8. A time measuring device comprising an acoustical resonator oscillating at a frequency of over 300 cycles per second, and serving as a time-keeping standard; a motion transformer having a pawl fixedly attached to said resonator and engaging teeth of a ratchet wheel to transmit rotary impulses thereto for driving a gear train of a time indicator, a magnetic coupling between said ratchet wheel and gear train to smooth intermittent rotation and transform same into at least approximately continuous rotary motion, said magnetic coupling comprising a driving wheel having permanently magnetized poles surrounding coaxially the axis of said ratchet wheel, the number of teeth of said ratchet wheel being greater than ten times the number of poles of the driving wheel, and a driven wheel having permanently magnetized poles disposed around its periphery and arranged adjacent said driving wheel so as to bring together the effective range of some poles of one wheel within effective range of some poles of the other wheel.

9. Device according to claim 8, wherein said driving wheel is formed as the shaft of said ratchet Wheel and consists of a high magnetic strength material, transversely magnetized with at least one pair of different poles.

10. Device according to claim 9, wherein said ratchet wheel has a rim made of copper-beryllium alloy and surrounds the axis constituting the driving wheel of the magnetic coupling.

11. Device as set forth in claim 1, wherein a permanently magnetized yoke is disposed adjacent one end of each of the shafts of said driving wheel and said driven wheel, so as to magnetize both said wheels by different poles, to attract said shafts against an axially directed bearing surface, and thereby avoid their axial movement.

12. Device as set forth in claim 1, wherein a permanently magnetized yoke is disposed adjacent one end of each of the shafts of said driving wheel and said driven Wheel, so as to magnetize both said wheels by different poles, to attract said shafts against an axially directed bearing surface, and thereby avoid their axial movement, provided with a second permanently magnetized yoke disposed between said shafts to increase the magnetic flux thereof.

13. Device as set forth in claim 1, wherein a permanently magnetized yoke is disposed between the shafts of said driving wheel and said driven wheel, so as to magnetize both said wheels by different poles, and a second yoke of soft magnetic material is provided adjacent one end of each of said shafts.

RICHARD B. WILKINSON, Primary Examiner E. C. SIMMONS, Assistant Examiner US. Cl. X.R. 74126 

